A process for analysing an electroencephalogram signal representative of activity of a brain, including: i) generating coefficient data for a signal representation of a portion of said signal； ii) generating first gain data representing an average amplitude of an output signal generated based on said signal representation and said coefficient data； iii) generating second gain data representing an average amplitude of said portion； and iv) generating, based on said first gain data and said second gain data, brain state data representing subcortical activity of said brain.
